Managing (?) older plantings of raspberries and blackberries

In our raspberry trials in the NC mountains, where raspberries are adapted and are capable of producing good crops, we have seen productivity decline after the 5th year of fruit production. While in the peidmont areas, we see a dramatic decline in the 2nd year of fruit production of raspberries (they are not adapted to the region). Blackberries on the other hand, tend to be more adapted and will live longer in most regions of the state. However, how long they will last is not known. In North Carolina and other states in the Southern US a recent rise in acreage of blackberries occurred in the past few years and as these plantings age, we need to monitor them to determine how long they will be productive both in terms of fruit and profits.

In the southern US, heat, drought, insects, diseases, if not controlled can take their toll on the productivity of a blackberry and raspberry field. Likewise, plant and soil health needs to be monitored in order to provide a plant with optimal nutrition.  Because this is a fairly new industry, we don't have long term experiences with the crop, however, below are a list of things to think about and address as needed as your plantings age.

Observation of annual growth. Growers should keep good records of individual fields and compare productivity from year-to-year. In addition to yield records, the plants health can be monitored by looking number of canes/plant, cane diameter,  and number of fruiting laterals. You do not need to count each of these, but a picture taken at the same spot in the field each year could help you identify any issues.

Diseases and insects. There is a long list of diseases that can negatively impact  blackberry or raspberry plant health.  In fields that are lightly managed, I most often see cane blight and viruses, and borers negatively impact productivity. 

Weeds. Perennial weeds harder to control over time and annual weeds will compete with crop. Both will impact productivity if left unchecked.

Fertility. There is no known long term research for caneberry fertility in the southern US. However, routine soil and plant tissue samples will help you determine needs and adjustments. Tissue samples should be taken each year and sent for evaluation. In NC, samples should be taken after fruit harvested from the plants. Leaves from the 3-5th node of the primocane plant should be taken and sent to NCDA and they will make recommendations for the following season. Keep your records so you can see if there are trends in your fields. Below are the recommended levels of macro and micronutrients.

Yield and prifitabilty. Good yield records for each field should be taken every year. A simple comparison each year will be your most useful indicator of planting productivity over time. Based on a budget developed at NC State University, when a grower is getting $14/flat, a 10% reduction in yield, their returns fall from $6036 to $4359/acre (see blue font below). You can get a copy of this budget and play with the inputs (any boxes that are blue can be edited).  http://ncsu.edu/enterprises/blackberries-raspberries/management/blackberry-raspberry-budgets-pricing/

Estimated Returns per Acre for Commercial Blackberry Production
for Varying Yields and Wholesale Prices per Flat.  Total yield 19,000lbs/acre, 80% marketable, so net of 15,200 marketable lbs/acre.
	Wholesale Market ($/flat)	Marketable Flats per Acre
		1,621	2,027	2,533	3,040	3,648
	$8.96	($8,173)	($7,533)	($6,732)	($5,932)	($4,971)
	$11.20	($4,542)	($2,993)	($1,058)	$878	$3,200
	$14.00	($2)	$2,682	$6,036	$9,390	$13,415
	$16.80	$4,538	$8,356	$13,129	$17,902	$23,629
	$20.16	$9,986	$15,166	$21,641	$28,116	$35,887

Estimated Returns per Acre for Commercial Blackberry Production
for Varying Yields and Wholesale Prices per Flat. Total yield is 17,100 lbs/acre, 80% marketable yield, so net of $13,600 lbs/acre.
	Wholesale Market ($/flat)	Marketable Flats per Acre¹
		1,459	1,824	2,280	2,736	3,283
	$8.96	($8,429)	($7,853)	($7,133)	($6,412)	($5,548)
	$11.20	($5,161)	($3,767)	($2,025)	($283)	$1,807
	$14.00	($1,075)	$1,340	$4,359	$7,377	$11,000
	$16.80	$3,011	$6,447	$10,743	$15,038	$20,193
	$20.16	$7,914	$12,576	$18,403	$24,231	$31,224